Method for producing high purity nickle, high purity nickle, sputtering target comprising high purity nickel, and thin film formed by using said spattering target

ABSTRACT

Upon performing electrolysis with a solution containing nickel as the electrolytic solution, anolyte is adjusted to pH 2 to 5; impurities such as iron, cobalt and copper contained in the anolyte are eliminated by combining any one or two or more of the methods among adding an oxidizing agent and precipitating and eliminating the impurities as hydroxide, eliminating the impurities through preliminary electrolysis, or adding Ni foil and eliminating the impurities through displacement reaction; impurities are thereafter further eliminated with a filter; and the impurity-free solution is employed as catholyte to perform the electrolysis. The present invention relates to a simple method of performing electrolytic refining employing a solution containing nickel from nickel raw material containing a substantial amount of impurities, and provides technology on efficiently manufacturing high purity nickel having a purity of 5N (99.999 wt %) or more.

TECHNICAL FIELD

[0001] The present invention pertains to a method of manufacturing highpurity nickel having a purity of 5N (99.999 wt %) or more throughelectrolytic refining employing a solution containing nickel, such highpurity nickel, a sputtering target formed from the high purity nickel,and a thin film formed with the sputtering target.

BACKGROUND ART

[0002] Generally speaking, high purity nickel is required to reduce, asmuch as possible, alkali metals, radioactive elements, transition metalelements and gas components, and is widely used particularly as asputtering target material for forming VLSI electrodes and wiring, orfor forming magnetic thin films.

[0003] Alkali metals such as Na and K easily move within the gateinsulation film, and cause deterioration of the MOS-LSI interfacialquality. Radioactive elements such as U and Th cause soft errors ofelements with the emitted a rays. Meanwhile, transition metal elementssuch as Fe also cause trouble at the interface bonding area.

[0004] Further, gas components such as carbon and oxygen are notpreferable in that they cause the generation of particles duringsputtering.

[0005] In general, when manufacturing high purity nickel of a 5N level,it is standard to refine the solution through ionic exchange or solventextraction, and obtain high purification by further performingelectrolytic winning or electrolytic refining thereto. Nevertheless,there were problems of inefficiency in that the steps in the methodadopting the foregoing solvent extraction process are complex, and it isnecessary to give consideration to the safety of the extract agent sincea special solvent must be used.

[0006] Although it is also possible to consider a relatively simplemethod of performing electrolysis employing a solution containing nickelupon manufacturing high purity nickel of a 5N level, it could notnecessarily be said that the employment of processes such as theforegoing solvent extraction are efficient.

DISCLOSURE OF THE INVENTION

[0007] An object of the present invention is to provide a simple methodof performing electrolysis employing a solution containing nickel fromnickel raw material containing a substantial amount of impurities suchas iron, carbon, oxygen and so on, and providing technology onefficiently manufacturing high purity nickel having a purity of 5N(99.999 wt %) or more from such raw material.

[0008] In order to overcome the foregoing problems, the presentinventors have discovered that high purity nickel can be manufacturedefficiently by eliminating impurities such as iron from anolyte of asolution containing nickel as hydroxide, and employing the impurity-freesolution as catholyte.

[0009] Based on the foregoing discovery, the present invention provides:

[0010] 1. A manufacturing method of high purity nickel, wherein, uponperforming electrolysis with a solution containing nickel as theelectrolytic solution, anolyte is adjusted to pH 2 to 5; impurities suchas iron, cobalt and copper contained in the anolyte are eliminated bycombining any one or two or more of the methods among adding anoxidizing agent and precipitating and eliminating the impurities ashydroxide, eliminating the impurities through preliminary electrolysis,or adding Ni foil and eliminating the impurities through displacementreaction; impurities are thereafter further eliminated with a filter;and the impurity-free solution is employed as catholyte to perform theelectrolysis;

[0011] 2. A manufacturing method of high purity nickel according toclaim 1, wherein an anode and cathode are partitioned with a diaphragm;anolyte is intermittently or consecutively extracted; an oxidizing agentis added thereto so as to precipitate impurities such as iron ashydroxide; impurities are further eliminated with a filter; and theimpurity-free solution is intermittently or consecutively added to thecathode side;

[0012] 3. A manufacturing method of high purity nickel according toclaim 1, wherein an anode and cathode are partitioned with a diaphragm;anolyte is intermittently or consecutively extracted; impurities such asiron, cobalt and copper are eliminated by performing preliminaryelectrolysis to this anolyte; impurities are further eliminated with afilter; and the impurity-free solution is intermittently orconsecutively added to the cathode side;

[0013] 4. A manufacturing method of high purity nickel according toclaim 1, wherein an anode and cathode are partitioned with a diaphragm;anolyte is intermittently or consecutively extracted; impurities such asiron, cobalt and copper are eliminated through displacement reaction byadding nickel foil to this anolyte; impurities are further eliminatedwith a filter; and the impurity-free solution is intermittently orconsecutively added to the cathode side;

[0014] 5. A manufacturing method of high purity nickel according to eachof claims 1 to 4, wherein activated carbon is employed as the filter;

[0015] 6. A manufacturing method of high purity nickel according to eachof claims 1 to 5, wherein the concentration of iron within theelectrolytic solution after filtering is 1 mg/L or less;

[0016] 7. A manufacturing method of high purity nickel according to eachof claims 1 to 6, wherein the electrolytic nickel obtained throughelectrolysis is subjected to vacuum melting such as electron beammelting;

[0017] 8. High purity nickel that is 5N (99.999 wt %) or more excludinggas components in which as impurities O:30 wtppm or less and C,N,S,P,Fare respectively 10 wtppm or less; a target formed from the high puritynickel; and a thin film formed through sputtering employing the target;and

[0018] 9. High purity nickel manufactured according to claims 1 to 7that is 5N (99.999 wt %) or more excluding gas components in which asimpurities O:30 wtppm or less and C,N,S,P,F are respectively 10 wtppm orless; a target formed from the high purity nickel; and a thin filmformed through sputtering employing the target.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019]FIG. 1 is a diagram showing the outline of the electrolysisprocess.

BEST MODE FOR CARRYING OUT THE INVENTION

[0020] Employing an electrolytic bath 1 shown in FIG. 1, a massivenickel raw material 2 of a 4N level is added to an anode basket 3 andmade an anode 5, and nickel or the like is employed as a cathode 4 forperforming electrolysis. The nickel raw material mainly contains a greatamount of iron, carbon, oxygen, and so on.

[0021] Electrolysis is performed under the conditions where the bathtemperature is 10 to 70° C., nickel concentration is 20 to 120 g/L, andcurrent density is 0.1 to 10 A/dm². The productivity deteriorates whenthe current density is less than 0.1 A/dm², and nodules are generatedwhen it exceeds 10 A/dm², which is not preferable since the anode 5 andcathode 4 will contact each other, and, therefore, the current densityis set within the range of 0.1 to 10 A/dm².

[0022] The anode 5 and cathode 4 are partitioned with a diaphragm 6 andanolyte is intermittently or consecutively extracted. The anolyte isadjusted to pH 2 to 5. A cathode box is separated from the outersolution (anolyte) via the diaphragm. An oxidizing agent 7 is added tothe extracted anolyte in order to precipitate impurities such as iron,cobalt and copper as hydroxide. In other words, binary iron becometernary by the oxidizing agent 7, and is precipitated as Fe(OH)₃.Hydrogen peroxide, nitric acid, and so on may be used as the oxidizingagent 7.

[0023] Moreover, the extracted anolyte may be added to a preliminaryelectrolytic bath in order to eliminate impurities such as iron, cobaltand copper through electrolysis.

[0024] Furthermore, the extracted anolyte may be added to a displacementbath so as to perform displacement with impurities such as iron, cobaltand copper in the electrolytic solution using nickel foil, and therebyeliminating such impurities.

[0025] Although FIG. 1 shows a process of adding an oxidizing agent,this process 7 can be substituted with preliminary electrolysis or thedisplacement method in order to facilitate elimination of impurities.

[0026] Impurities can also be eliminated by respectively combining theforegoing oxidizing agent, preliminary electrolysis or displacementmethod.

[0027] Impurities such as these sediments are eliminated with a filter8. It is preferable that activated carbon is used as the filter. Theactivated carbon filter 8 yields an effect of eliminating organic mattereluted from the container or the like in addition to impurities such asthe foregoing precipitated oxides. According to the above, theconcentration of iron within the electrolytic solution can be made 1mg/L or less.

[0028] After the elimination of impurities, this solution isintermittently or consecutively introduced to the cathode side, and usedas catholyte for performing electrolytic refining.

[0029] The current efficiency will be 80 to 100%. According to theabove, electrolytic nickel (deposited to the cathode) having a purity of5N is obtained. In other words, the purity is 5N (99.999 wt %) excludinggas components, in which as impurities O:30 wtppm or less andC,N,S,P,F,H are respectively 10 wtppm or less.

[0030] Moreover, the electrolytic nickel obtained through electrolysismay be subjected to vacuum melting such as electron beam melting. Alkalimetals such as Na and K as well as other volatile impurities and gascomponents can be effectively eliminated with such vacuum melting.

[0031] Further, since ion exchange resin and solvent extraction are notused in the present invention, organic matter will not get mixed in, andit is thereby possible to suppress impurity elements arising fromorganic solvents.

EXAMPLES AND COMPARATIVE EXAMPLES

[0032] The present invention is now described with reference to theExamples and Comparative Examples. These Examples are merelyillustrative, and the present invention shall in no way be limitedthereby. In other words, the present invention shall include, within thescope of its technical spirit, any and all modes or modifications otherthan the Examples of this invention.

Example 1

[0033] With the electrolytic bath shown in FIG. 1, 1 kg of massivenickel raw material of a 4N level was made an anode, and electrolysiswas performed to a cathode with a nickel plate of a 2N level. Thecontent of impurities in the raw material is shown in Table 1. Thenickel raw material mainly contains a great amount of iron, carbon,oxygen, and so on.

[0034] Electrolysis was performed for 40 hr under a bath temperature of50° C., in which 1 mol/L of hydrofluoric acid was added to a sulfuricacid electrolytic solution, a nickel concentration of 50 g/L and acurrent density of 2 A/dm².

[0035] The solution pH was adjusted to 2. Here, anolyte wasintermittently extracted. Hydrogen peroxide (H₂O₂) was added to theextracted anolyte to change the binary iron to ternary iron, andimpurities such as iron were precipitated as hydroxide Fe(OH)₃.

[0036] Further, impurities such as these sediments were eliminated withan activated carbon filter. According to the above, it was possible tomake the concentration of iron within the electrolytic bath to be 1 mg/Lor less.

[0037] After the elimination of impurities, this solution wasintermittently introduced to the cathode side; that is, within thecathode basket, and used as catholyte to perform electrolysis.

[0038] Approximately 1 kg of electrolytic nickel (deposited to thecathode) was obtained. The purity reached 5N. In other words, the puritywas 5N (99.999 wt %) or more excluding gas components, in which asimpurities O:30 wtppm or less and C,N,S,P,F were respectively 10 wtppmor less. TABLE 1 Fe O C N S P F H Raw 50 200 50 10 10 10 10 10 MaterialExample 1 2 20 <10 <10 <10 <10 <10 <10 Example 2 1 <10 <10 <10 <10 <10<10 <10 Comparative 50 60 <10 <10 <10 <10 <10 <10 Example 1 (wtppm)

Example 2

[0039] With the same electrolytic bath as Example 1, massive nickel rawmaterial of a 4N level was made an anode, and electrolysis was performedto a cathode with a nickel plate of a 3N level.

[0040] Electrolysis was performed for 40 hr under a bath temperature of30° C., with a hydrochloric acid electrolytic solution, a nickelconcentration of 80 g/L and a current density of 5 A/dm².

[0041] As with Example 1, the solution pH was adjusted to 2. Here,anolyte was intermittently extracted. Hydrogen peroxide (H₂O₂) was addedto the extracted anolyte to change the binary iron to ternary iron, andimpurities such as iron were precipitated as hydroxide Fe(OH)₃.

[0042] Further, impurities such as these sediments were eliminated withan activated carbon filter. According to the above, it was possible tomake the concentration of iron within the electrolytic bath to be 1 mg/Lor less.

[0043] After the elimination of impurities, this solution wasintermittently introduced to the cathode side; that is, within thecathode basket, and used as catholyte to perform electrolysis.

[0044] Approximately 1 kg of electrolytic nickel (deposited to thecathode) was obtained. Electron beam melting was further performed tothis electrolytic nickel. Electron beam melting was performed under theconditions of 1A, 30 kW, and degree of vacuum of 2 to 5×10⁻⁴ mmHg. Theforegoing results are similarly shown in Table 1.

Comparative Example 1

[0045] With the electrolytic bath shown in FIG. 1, 1 kg of massivenickel raw material of a 4N level was made an anode, and electrolysiswas performed to a cathode with a nickel plate of a 3N level. Thecontent of impurities in the raw material is shown in Table 1.

[0046] Electrolysis was performed for 40 hr under a bath temperature of50° C., in which 1 mol/L of hydrofluoric acid was added to a sulfuricacid electrolytic solution, a nickel concentration of 50 g/L and acurrent density of 2 A/dm².

[0047] The solution pH was adjusted to 2. Here, anolyte was notextracted and electrolysis was continued.

[0048] Approximately 1 kg of electrolytic nickel (deposited to thecathode) was obtained.

[0049] The foregoing results are similarly shown in Table 1.

[0050] As shown in Table 1, with Example 1, it was possible to make theraw material iron from 50 wtppm to 2 wtppm, oxygen from 200 wtppm to 20wtppm, carbon from 50 wtppm to less than 10 wtppm, C, N, S, P, F from 10wtppm to less than 10 wtppm, respectively.

[0051] Moreover, in Example 2, it was possible to make iron lwtppm,oxygen less than 10 wtppm, and other impurities less than 10 wtppm.

[0052] Contrarily, in Comparative Example 1, although it was possible tomake C, N, S, P, F from 10 wtppm to less than 10 wtppm, respectively,iron was 50 wtppm and oxygen was 60 wtppm, and refining effects wereinferior in comparison to the Examples, and, in particular, theelimination of iron was difficult.

Example 3

[0053] 1 kg of massive nickel raw material of a 3N level was made ananode, and electrolysis was performed to a cathode with an aluminumplate of a 2N level. The content of impurities in the raw material isshown in Table 2. The nickel raw material mainly contains a great amountof iron, carbon, copper, carbon, oxygen, and so on.

[0054] Electrolysis was performed for 25 hr under electrolyticconditions of a bath temperature of 40° C., in which 1 mol/L ofhydrochloric acid was added to a sulfuric acid electrolytic solution, anickel concentration of 100 g/L and a current density of 3 A/dm².

[0055] The solution pH was adjusted to 2.5. Here, anolyte wasintermittently extracted. Electrolysis was performed to the extractedanolyte in a preliminary electrolytic bath under a current density of0.1 A/dm², and impurities such as iron, cobalt and copper wereeliminated.

[0056] Further, organic matter within the electrolytic solution waseliminated with an activated carbon filter. According to the above, itwas possible to make the concentration of iron, cobalt and copper withinthe electrolytic bath to be 1 mg/L or less.

[0057] After the elimination of impurities, this solution wasintermittently introduced to the cathode side; that is, within thecathode basket, and used as catholyte to perform electrolysis.

[0058] As a result, approximately 1.1 kg of electrolytic nickel wasobtained. The purity reached 5N. In other words, the purity was 5N(99.999 wt %) or more excluding gas components, in which as impuritiesO:20 wtppm or less and C,N,S,P,F were respectively 10 wtppm or less. Theforegoing results in comparison to the raw materials are shown in Table2.

Example 4

[0059] 1 kg of massive nickel raw material of a 3N level was made ananode, and electrolysis was performed to a cathode with a titanium plateof a 2N level. The content of impurities in the raw material is shown inTable 2. The nickel raw material mainly contains a great amount of iron,carbon, copper, carbon, oxygen, and so on.

[0060] Electrolysis was performed for 50 hr under electrolyticconditions of a bath temperature of 60° C., in which 1 mol/L ofhydrochloric acid was added to a sulfuric acid electrolytic solution, anickel concentration of 100 g/L and a current density of 1.5 A/dm².

[0061] The solution pH was adjusted to 2.7. Here, anolyte wasintermittently extracted. The extracted anolyte was replaced withimpurities within the electrolytic solution with Ni foil of a 2N levelin a displacement bath, and impurities such as iron, cobalt and copperwere eliminated.

[0062] Further, organic matter within the electrolytic solution waseliminated with an activated carbon filter. According to the above, itwas possible to make the concentration of iron, cobalt and copper withinthe electrolytic bath to be 1 mg/L or less.

[0063] After the elimination of impurities, this solution wasintermittently introduced to the cathode side; that is, within thecathode basket, and used as catholyte to perform electrolysis.

[0064] As a result, approximately 1.1 kg of electrolytic nickel wasobtained. The purity reached 5N. In other words, the purity was 5N(99.999 wt %) or more excluding gas components, in which as impuritiesO:20 wtppm or less and C,N,S,P,F were respectively 10 wtppm or less. Theforegoing results in comparison to the raw materials are shown in Table2.

Example 5

[0065] During the steps of foregoing Example 3, anolyte wasintermittently extracted, electrolysis was performed to the extractedanolyte in a preliminary electrolytic bath under a current density of0.1 A/dm², and impurities such as iron, cobalt and copper wereeliminated under the same conditions as the displacement reaction in thedisplacement bath of Example 4 (combination of preliminary electrolysisand displacement reaction).

[0066] And, with the same steps as Example 3 excluding the foregoingstep, approximately 1.1 kg of electrolytic nickel was obtained. As aresult, the purity was 5N or more excluding gas components, in which asimpurities O:10 wtppm or less and C,N,S,P,F were respectively 10 wtppmor less. The foregoing results in comparison to the raw materials areshown in Table 2. TABLE 2 Fe Co Cu O C N S P F H Raw 30 20 10 150 40 1010 10 10 10 Material Example 3 3 1 1 20 <10 <10 <10 <10 <10 <10 Example4 5 2 1 20 <10 <10 <10 <10 <10 <10 Example 5 1 1 0.3 10 <10 <10 <10 <10<10 <10 (wtppm)

[0067] According to the above, with the method of the present inventionof partitioning the anode and cathode with a diaphragm, intermittentlyor consecutively extracting the anolyte, adding an oxidizing agentthereto to precipitate impurities such as iron as hydroxide, furthereliminating impurities with a filter, and performing electrolysis byintermittently or consecutively adding the impurity-free solution to thecathode side, it is clear that iron can be effectively eliminated, and,upon obtaining high purity nickel, that it is a simple yet extremelyeffective method.

EFFECT OF THE INVENTION

[0068] As described above, provided is a simple method of performingelectrolytic refining with a solution containing nickel from a nickelraw material containing a substantial amount of impurities such as iron,carbon, oxygen, and so on. Pursuant to the improvement of a simplemanufacturing process, the present invention yields a significant effectof enabling the efficient manufacture of high purity nickel having apurity of 5N (99.999 wt %) or more from the foregoing raw material.

What is claimed is:
 1. A manufacturing method of high purity nickel,wherein, upon performing electrolysis with a solution containing nickelas the electrolytic solution, anolyte is adjusted to pH 2 to 5;impurities such as iron, cobalt and copper contained in the anolyte areeliminated by combining any one or two or more of the methods amongadding an oxidizing agent and precipitating and eliminating saidimpurities as hydroxide, eliminating said impurities through preliminaryelectrolysis, or adding Ni foil and eliminating said impurities throughdisplacement reaction; impurities are thereafter further eliminated witha filter; and the impurity-free solution is employed as catholyte toperform said electrolysis.
 2. A manufacturing method of high puritynickel according to claim 1, wherein an anode and cathode arepartitioned with a diaphragm; anolyte is intermittently or consecutivelyextracted; an oxidizing agent is added thereto so as to precipitateimpurities such as iron as hydroxide; impurities are further eliminatedwith a filter; and the impurity-free solution is intermittently orconsecutively added to the cathode side.
 3. A manufacturing method ofhigh purity nickel according to claim 1, wherein an anode and cathodeare partitioned with a diaphragm; anolyte is intermittently orconsecutively extracted; impurities such as iron, cobalt and copper areeliminated by performing preliminary electrolysis to this anolyte;impurities are further eliminated with a filter; and the impurity-freesolution is intermittently or consecutively added to the cathode side.4. A manufacturing method of high purity nickel according to claim 1,wherein an anode and cathode are partitioned with a diaphragm; anolyteis intermittently or consecutively extracted; impurities such as iron,cobalt and copper are eliminated through displacement reaction by addingnickel foil to this anolyte; impurities are further eliminated with afilter; and the impurity-free solution is intermittently orconsecutively added to the cathode side.
 5. A manufacturing method ofhigh purity nickel according to each of claims 1 to 4, wherein activatedcarbon is employed as the filter.
 6. A manufacturing method of highpurity nickel according to each of claims 1 to 5, wherein theconcentration of iron within the electrolytic solution after filteringis 1 mg/L or less.
 7. A manufacturing method of high purity nickelaccording to each of claims 1 to 6, wherein the electrolytic nickelobtained through electrolysis is subjected to vacuum melting such aselectron beam melting.
 8. High purity nickel that is 5N (99.999 wt %) ormore excluding gas components in which as impurities O:30 wtppm or lessand C,N,S,P,F are respectively 10 wtppm or less; a target formed fromsaid high purity nickel; and a thin film formed through sputteringemploying said target.
 9. High purity nickel manufactured according toclaims 1 to 7 that is 5N (99.999 wt %) or more excluding gas componentsin which as impurities O:30 wtppm or less and C,N,S,P,F are respectively10 wtppm or less; a target formed from said high purity nickel; and athin film formed through sputtering employing said target.